## 1.2.a Discrete-time signals

#### Discrete-time signals

- Discrete-time signal:= A sequence of complex numbers
- Dimension = 1 (for now)
- Notation: x[n] where n is an integer
- Two-sided sequences: x: \mathbb{Z} \rightarrow \mathbb{C}
- n is one-dimensional “time”.
- Analysis: Periodic measurement approach
- Discrete-time signals can be created by an analysis process where we take periodic measurements of a physical phenomenon.

- Synthesis: Stream of generated samples

#### Delta signal

Every sample is equal to 0 except for one sample equal to 1 if n is 0. The sound of the movie clapper is used to find the start time of a scene.

- x[n]=1 if n=0
- x[n]=0 if n \neq 0

#### Unit step signal

- x[n]=0 if n<0
- x[n]=1 if n \geq 0